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A “walking” rock tagged with a GPS tracker on a cold, desert morning. Photograph by Mike Hartmann

Some scientists use GPS locations to keep track of wide-ranging sharks. Others attach GPS tags to observe the movements of reclusive snow leopards. And then there are the guys who use the technology to study the movements of rocks.

Yes, rocks. But not just any old rocks.

These are the “sliding rocks” or “sailing stones” of Death Valley. First documented by miners back in the 1900s, these rocks range from pebbles to 600-pound (272-kilogram) boulders and seem to move of their own accord. The only evidence of their activity is a series of long, perplexing trails left in the valley’s dried mud. (Related: “Stranger Than Nature: Death Valley’s Moving Rocks.”)

Scientists have been trying to solve the mystery of the sliding rocks since 1948, and have since proposed all manner of explanation: dust devils, flooding, ice sheets, hurricane-force winds, and algal films.

A sliding rock in Death Valley leaves behind a trail through the dried mud. Photograph by Michael Melford, National Geographic Creative

But thanks to new photographic and meteorological evidence presented by Richard Norris of the Scripps Institution of Oceanography and James Norris of Interwoof, we may finally have a conclusive answer as to what makes the stones stir. The researchers’ findings were published today in the journal PLOS ONE.

A Goldilocks Phenomenon

According to Norris, a geological oceanographer and paleontologist, Death Valley’s rocks move under a delicate mix of water, ice, sun, and wind. Norris and his cousin were able to document the rock movements by inserting GPS tags into chunks of limestone and syncing their movements with readings taken from a custom-built weather station.

Unlike one of the previous explanations, which had thick ice capturing the rocks and carrying them along like a miniature glacier, Norris said their evidence shows that thin ice floes break up and pile against the rocks. This creates enough friction to cause the rocks to skim across the muddy surface of a temporary pond. If you were there to see it, the rocks would look like ice-breaker ships plowing through sea ice—though in this instance, it’s the ice that’s moving the ships.

But the conditions have to be just right, what Norris called a sort of Goldilocks phenomenon. If the ice is too thick, or the day is too sunny, or the wind isn’t steady enough, then nothing happens.

“The process of ice breaking up and shoving rocks around happens every year if you go up into Saskatchewan or Ontario, but you don’t normally associate it with a hot, dry place like Death Valley,” said Norris. “And yet here’s the same kind of process unfolding occasionally—very occasionally—in this place that we associate with a very different kind of climate.”

Watching Rocks Slither

Scientists have long known that whatever it is that causes the stones to move, it doesn’t happen very often. In fact, the mudflat where you’ll find the rocks and their trails, called Racetrack Playa, can go a decade or more without showing any new signs of movement.

That’s why it’s a fantastic coincidence that the researchers not only recorded evidence of rocks shifting by way of their GPS tags, but also witnessed the phenomenon in person this past winter.

“There was this crackling sound or popping sound all over the playa,” said Norris. “One moment it was quiet, and the next moment it was popping everywhere as the ice began to break up, and I said to my cousin, ‘This is it! We’re actually seeing this whole thing happen!’”

In all likelihood, the trails created that day will be frozen in time for another decade or more. That is, until another rain shower pours down and erases the stones’ trails like a giant Etch A Sketch.

Comments

One could believe that the rocks are dancing — of course! They ROCK and roll…

Bob Davis

Planet Earth

September 7, 2014, 1:06 pm

The mystery may be gone. However the knowledge exceeds the mystery. It is still fascinating. You guys did a great job for mankind, science, and knowledge.

Barry Vessell

United States

September 2, 2014, 12:53 pm

Why shouldn’t people walk on this land, is it because of the phenomenon? or is this land sacred? just wondering.
Its the first Ive heard of this place.

Dan Elliott Jr.

San Jose, CA 95124

September 1, 2014, 7:11 pm

Inasmuch as us stupid tourists are allowed to walk on the playa to view the rocks ourselves up close, us heathen tax-payers that pay the grants to these scientists that cannot think-up a legitimate way to support themselves, here we all are, perplexed.

Kurb

September 1, 2014, 12:16 am

Ahmad, the video clearly shows North-South motion of a rock, although I’m sure East-West and any linear combination of North-South and East-West motion occur…

Michael Sharon

Norwood New Jersey 07648

August 30, 2014, 7:48 pm

No one mentioned Borax,Death valley is loaded with it and it is used in soap

josé silva

Lisbon

August 30, 2014, 4:18 pm

Yes, just like faulting kinematic shear sense;

Jeremy

August 29, 2014, 7:35 am

The researcher got one thing wrong. There is nothing boring about this whatsoever. Excellent research!

*Confidential*

August 28, 2014, 10:47 pm

Wind? Ice? Mud? No. Aliens…..

*Confidential*

August 28, 2014, 10:46 pm

aliens….

Playa Jim

Southern California

August 28, 2014, 7:36 pm

First, I am one of the researchers who made this discovery.
To answer the question if we walked on the muddy playa, no of course not, we have been working closely with the Park service, and would not endanger our research permit by irresponsible behavior like that. We too we taken aback by the many footprints left by thoughtless visitors this last winter.
Where to get the job, funny that, this was not part of our jobs, we did it as citizen scientists, interested in the problem, and curious enough to make the effort to find out what was going on. Dug into our on pockets to finance it too, not a cent in grant money.
As far as answering the mystery and the loss of wonder at it all, yea we feel that too, however knowledge is also important to mankind. Thanks to all for your interest in this amazing place.

Darren White

United States

August 28, 2014, 6:11 pm

Grimlins are doing it….and because its a timelaps and not an actual video the images that were shot just don’t have the Gremlins in them… pretty simple….I mean you can take a timelapse of anything and just not include yourself in the image as your moving it…. J/K

Dave greenberg

August 28, 2014, 3:12 pm

Similar to snow rollers wich we had here this past winter. Just the perfect combinations of conditions to create them and they are very rare also

Charles Britzman

United States

August 28, 2014, 2:50 pm

It’s about time ! The technology for nailing this one down has been around a long time. Thanks to the researchers for getting serious about this at last.
I can have a layman’s understanding of the basic geology of the Sierra Nevada, and still stand on Mt Whitney or Mt Langley with a full heart and shining spirit. Same with the Racetrack’s rocks. For me, they STILL rock !

Dogacan Jeremy Edens

Adana, Turkey

August 28, 2014, 1:07 pm

It is possible that the rocks have a component that condenses at night and suddenly heats in the morning which makes the moisture condense on the rock that makes the bottom slippery and gradually makes it slide. But it really is a phenomenon.

Aslam Syed

Kirther, Pakistan

August 28, 2014, 7:40 am

World is amazing !

Paul Scutts

August 28, 2014, 6:22 am

Apollo 18.

Ariel RG

August 27, 2014, 10:45 pm

Its interesting to know the many factors that move those rocks.
Btw, The pioneers used to ride bigger rocks for miles!

Jeff Sullivan

United States

August 27, 2014, 10:02 pm

I hope that the researchers didn’t walk on the playa while it was wet.

There was an absurd amount of damage to the playa in the form of footprints in early 2014, much more than I’ve seen in the past 10 years.

Sylvia Smith

August 27, 2014, 7:19 pm

My theory – rocks must have magnetic properties which is following the under ground magma flow?

Joe

Tucson

August 27, 2014, 6:59 pm

First, I want one of those jobs, investigating stuff like this! Where do I apply?
And second, while I think the research is really very good and well thought out, and the results seem to be pretty conclusive…I’m a bit disappointed. My wife and I were out at Racetrack Playa a couple of years ago, and the mystery of it all (at that time, anyway) was the best part.
The enigma of Racetrack Playa…now gone. Somehow I feel like I’ve lost a good friend. Sigh.

Aaron M

August 27, 2014, 6:20 pm

Looks like these are the guys who put shoe-steps all over the playa!!!!

(Probably not, but they do show a shot of them on the playa while it’s all muddy)

Ahmad

LA

August 27, 2014, 4:21 pm

I have seen this as a child elsewhere in the world and I often wondered who is pushing these rocks in the middle of nowhere and why? If the authors claim the movement is due to the wind, ice, water, sun and etc. then why is it that the rocks in the photos above seem to be moving either eastward or towards the west. Perhaps this phenomenon can be best explained with keeping in mind the earth’s rotation.

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